The self-propelled hydraulic inverting bridge formwork adopts mechatronics and hydraulic integration design, equipped with multi-functional automatic walking device, front support, rear lateral movement mechanism, hydraulic self-balancing system, which can realize automatic vertical movement, rise and fall, and automatic horizontal movement, with a high degree of automation , Can adapt to a variety of construction work environment.
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The self-propelled hydraulic inverting bridge formwork is composed of the main body of the trestle bridge, hydraulic system, electrical control system, and walking system.
The main structure of the main bridge: 8 40b# I-beams are arranged in parallel along the longitudinal direction of the tunnel at the bottom of the bridge, 4 20# channel steels and 6 20b# I-beams are arranged horizontally along the tunnel on the bottom of the bridge, with box-shaped structures on both sides and the middle 25# I-shaped steel support connection. The hydraulic system includes various lifting cylinders and related hydraulic pump stations and pipelines; the electrical system is responsible for controlling the operation of each system, mainly composed of various relays, switches, circuit breakers, etc.
The traveling system is composed of a motor reducer, a transmission chain, a box body, a traveling wheel, etc. There are 4 groups, which are respectively placed on both sides of the end of the trestle body to realize the automatic walking of the trestle body. The walking device can realize horizontal and vertical walking, which is flexible and convenient.
In order to meet the requirements of movement, a mobile walking mechanism is set at both ends of the trestle bridge, and a limit warning device is set; when walking, the lifting and lowering of the slope bridge at both ends of the trestle bridge is completed by the hydraulic system actuator. The self-propelled hydraulic inverting bridge formwork is mainly composed of the main bridge, traveling device, hydraulic system, electrical system, limit device and alarm system. The trestle bridge is moved. When moving, it is driven by a motor and driven by a gear pinion to drive the walking wheel to move on the walking track. The working steps are as follows:
Start the main bridge lifting cylinder installed at the end of the trestle bridge to make the trestle bridge slope off the ground, and then with the cooperation of workers, drag the trestle bridge walking track forward. After the track is dragged to the end, shrink the main bridge lifting cylinder to start the traveling motor. The trestle moves forward on the track, after moving to the end of the track, repeat the above steps until the trestle is in place (the trestle's lateral movement is the same as this). After the trestle bridge is in place, the main bridge lifting cylinder is lifted up, so that the running wheels are not stressed. After being fixed, the front and rear slope bridges are put down.
According to the requirements of the construction schedule, the construction of the tunnel entering the invert position, in order to ensure that the invert construction continues and the slag from the tunnel excavation and the transportation of materials in the tunnel are not affected by the invert excavation, so the invert excavation slot is installed the trestle bridge will be constructed. After the strength of the poured invert concrete meets the traffic strength requirements, the trestle bridge can be pushed forward to the excavation groove at the bottom of the next tunnel, and then recycled. So as to realize the rapid and safe progress of tunnel construction.
Plan ahead of time the personnel, materials and machinery required for processing. The installation of the trestle is carried out by professional and technical personnel. When the hydraulic inverting bridge formwork is erected, the bottom slag of the front platform of the trestle must be removed before the trestle is advanced, and the foundation must have a certain bearing capacity. The back end is laid on the top surface of the filling; the front ramp of the trestle bridge should be firmly connected with the trestle platform to ensure the safety of erection. After the trestle bridge is erected and installed in place, safety nets must be hung outside the guardrails on both sides of the trestle bridge to prevent the falling of gravel from hurting the operators of the inverted arch construction below; obvious slow-moving warning signs should be set at the front and rear of the trestle bridge, and the trestle bridge surface should have anti-skid measures.
Before the trestle bridge is moved, erected and installed, the welding parts of the trestle bridge shall not have the phenomenon of welding seam falling off or welding seam cracking, and the supporting system shall be inspected to check whether the main beam and auxiliary components of the trestle bridge are cracked and deformed. If problems are found, the trestle shall not be carried out. Moving and erecting, the trestle can be moved and erected only after the processing is completed and the inspection is qualified.
Use an excavator or loader to set it in place, and walk on its own after it is in place: the inverted arch can only be moved after the strength of the filled concrete reaches the design requirements and the necessary protective measures must be taken. The movement must be slow to avoid damage to the quality of the finished concrete: trestle bridge When moving, full-time personnel must be assigned to uniformly command, and no one is allowed to stand in the trestle work area.
(1) The invert excavation is divided into left and right parts, and half of the excavation is carried out first.
(2) In the first cycle, first excavate the left or right inverted arch, and park the trestle on the side where there is no excavation: park the slag truck on the trestle, and excavate the excavator on the surface to be excavated When excavating from the front to the rear of the trestle bridge, the excavator has been parked on the elevation surface of the inverted arch, so as to ensure that the excavator can load the slag into the slag truck.
(3) After excavating one side, operate the trestle bridge to move the trestle bridge to the side that has been excavated, and also park the slag truck on the trestle bridge, and the excavator will excavate on the surface to be excavated. When excavating from the front end to the back end of the trestle bridge, the excavator has been stopped on the elevation surface of the invert, so as to ensure that the excavator can load the slag into the slag truck; at this time, the invert excavation and the invert lining can be carried out simultaneously.
(4) Repeat the above process to complete the next cycle of invert construction.
(1) Through the application of the trestle bridge in the tunnel, the materials and tools for the construction of the tunnel face can pass from the upper part of the trestle bridge, reducing the interference between excavation construction and invert construction: at the same time, the trestle bridge has a large span and is an inverted arch The construction provides a streamlined work surface: the trestle itself is convenient and quick to install, walks more flexible, and has a high level of mechanization. These are conducive to speeding up the tunnel construction speed and solving the schedule problem, especially for the long tunnel and the tight construction period, the benefit of ensuring the schedule is very obvious.
(2) Compared with the simple trestle bridge, the use of movable hydraulic inverting bridge formwork, although the cost of manufacturing or purchase increases, but because it provides enough space for inverting operations, it can effectively organize flow construction. Improve production efficiency and speed up, especially in the case of long tunnels, which will play a role in reducing engineering costs.
(3) Ensure the safety of construction workers under the trestle bridge. The hydraulic inverting bridge formwork made of section steel is stable in structure, safe and reliable; the mobile trestle reduces the interference between working procedures, and the structural safety is improved compared with the simple trestle.
(4) It is beneficial to ensure the quality of tunnel construction. Due to the use of the trestle bridge, it is guaranteed that the invert is poured in one time, which is beneficial to ensure the quality of the invert.
(1) Personnel operating the trestle bridge must be trained and qualified before they can carry out operations.
(2) When the hydraulic inverting bridge formwork is in place, pay attention to the flatness of the installation and the width of the installation to meet the design requirements to ensure the safety of the vehicle and the normal passage of vehicles with different wheel bases.
(3) The speed limit for vehicles passing through the trestle bridge should be determined according to the actual situation on site to ensure the stability and safety of the hydraulic inverting bridge formwork during work: construction personnel are prohibited from passing vehicles when working under the trestle bridge to ensure the safety of operators.
(4) Lay safety nets on the outside of the trusses on both sides of the trestle bridge to prevent the falling of gravel from hurting the construction operators below. The concrete and debris on the self-propelled hydraulic inverting bridge formwork should be cleaned up in time to keep the upper part of the trestle clean.
The application of hydraulic trestle has changed the existing tunnel invert construction organization mode. Under the premise of not affecting the tunnel face construction, the tunnel invert excavation, reinforcement binding, invert pouring and other operations are carried out at the same time to realize the excavation and invert the parallel operation of arch construction greatly saves construction time and improves the overall efficiency of tunnel construction.
Due to the automatic walking device, the trouble of manually moving the trestle bridge is reduced, the automation level of tunnel construction is improved, and the safety is enhanced. Become the technical basis for ensuring the quality, schedule, and cost control of the tunnel invert construction, and the technical basis for realizing the standardization of tunnel construction and the construction of humanized and civilized construction sites.
One of the most common characteristics of garden railroads is the timber trestle, a sight common in hilly terrain a century ago and still visible today in some out-of-the-way places. The complex lattice-work inevitably draws attention, no matter how big the trestle is. But it is neither as difficult nor as time-consuming to build a trestle as you might think. In fact, if you are going to have a raised railroad anyway, a trestle is one of the fastest and least expensive ways to fill the gap between the track and the terrain.
A trestle is made up of relatively simple components that are repeated over and over again. To build a trestle, you create a "jig," that is a carefully measured framework that helps you assemble the most important components quickly.
You will need:
The key component of any trestle is called a "bent." It is the vertical component you would see if you could look at the "cross-section" of a trestle. Generally a "bent" consists of 4-6 long vertical posts that spread out as they go from "top" to "bottom" and two or more horizontal "sills." Most garden railroaders build the trestle bents in their workshop, then assemble them in their garden once the rest of the track and roadbed has been laid.
Note on Staining Trestles: In August, , a reader asked how to stain the trestle, and I got input from several people, whose responses are in the appendix of the article. Some folks stain the wood before they build anything, some folks stain the bents after they're assembled, and some folks stain the whole thing at a time after it's assembled. And the chemicals folks use are "all over the map." But if you read that section before you start building bents in earnest, you may find a method that appeals to you. I put this note here in case you decide to stain your wood before you assemble your bents, so you can plan ahead.
Back to Building Trestle Bents - Trestle bent construction has been described in Garden Railways a few times, and there is a brief description in Jack Verducci's book How to Design and Build a Garden Railway. But I thought it might be worth spelling out a detailed step-by-step procedure that could be used even by people with relatively little skill and no tool more complicated than a table saw. (In a way this is a throwback to the earliest days of my site, when my New Boston and Donnels Creek pages had the central theme of "If even I can do this, anybody can.")
The most prominent parts of a trestle bent are the:
As an example, many railroads today are being built with Bill Logan's HDPE ladder-style roadbed. The result is a clean, open framework that both supports the track and looks good on top of a trestle or other bridge construction. You could "toenail" (angle) screws or nails through that roadbed right into the caps of your bents, if you wished, and many people have. But Bill's preferred solution is to add a strip of 3/4" x 3/4" HDPE lumber to the outside lower edge of the HDPE roadbed. Then he can shoot nails either down into the cap or up through the cap easily. When Bill is satisfied that the trestle will hold the track, he removes the temporary vertical supports. In the photo at the left, the vertical support is still there, but it was removed a few minutes after this photo was taken.
Some folks do build trestles that fully and independently support their track. To do that properly is outside the scope of this article, but you should know that it requires addition of "stringers" that run parallel to the rails and support the ties underneath. If you try this, you may want to add diagonal bracing between the bents to provide a more rigid overal structure. Folks who follow this approach typically build and assemble the whole trestle in the "shop" before the track is even installed; then they install the trestle in one piece and install the track on top of it. Many beautiful garden railroad trestles have been built this way.
In addition, you should think about what happens where the bottom of your trestle reaches the ground. The best case is not to have it touch soil at all; more than one garden railroader has had to replace part of a trestle that started rotting out from the ground up. My friend Wil Davis uses concrete bricks as "footers" for the bottom edge of his trestle. If you want to use a poured concrete base or those 8"x16" concrete blocks, disguised with gravel, that would work, too. Find out what folks in your area are doing successfully if you can.
However you decide to attach your trestle to your roadbed or to deal with the bottom edges, it's better to think this through now than later.
You'll also need to think about how you will provide cross-connections between bents once the bents are in place between your roadbed and your footer. In the title photo, they've obviously used long strips of wood that are thinner than the members that make up the trestles. A more diligent modeler may wish to follow prototype practices, having many cross-connectors that are only long enough to reach from one trestle bent to the next. While you're experimenting with the first few bents you've put together, get some scrap pieces and visualize how you will fasten the trestle bents together once they are installed.
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Using a single piece of wood to represent the crossbars simplifies construction. Separate, staggered crossbars provide visual interest.Many options for connecting bents have been tried by the "real" railroads.
Most garden railroaders don't add diagonal ("sway") bracing on the outside of the trestle. But it adds even more interest if you have time to do it. To the right is an example of a garden railroad trestle that uses a single strip of wood for the crossbars and adds sway bracing on top of the pieces. It is built by Dayton-area garden railroader Denny LaMusga and featured on the title graphic of our Pimer index page. Click for a bigger photo.
Denny's outside sway braces mechanically make the trestle more stable. It also camouflages the fact that the crossbars are all one piece. A diagram showing how the pieces interact is shown below to the right.
It's not hard to tell from looking at the table above why most garden railroaders choose 1/2". Still I would encourage anyone using 1:29 or 1:32 trains to consider 3/8" as long as it is mechanically feasible with the materials and tools at hand. Oversize timbers give a false impression of the relative size of Standard Gauge trains, making them look as much as 25% smaller than they should in relationship to their surroundings.
On D&RGW trestles, the sills (horizontal members) also tended to be 12" square, so the same cut pieces will do for those as for the posts. The top sill, also called a "cap," was usually 12" wide by 14" deep, but most modelers use the same dimensions as they use for the posts and other sills.
On the other hand, you sometimes have to work the the materials that are easily available to you. For my yet-unfinished project, I tried using some "Western" cedar fence boards, the kind you use if you're making a "dog-ear" fence from scratch, because I liked the color and the grain. When I started using them, I realized that they varied between 9/16" and 5/8" in depth. So if I do use these in "production mode" I will have to run each piece through the saw twice - once to cut it to width, and once to even out the depth. Then I realized why so many folks doing this just start with 2"x4" boards anyway.
Conversely, you may have come across a bunch of "tomato stakes" or something that are a little smaller than they "should be" to meet with D&RGW standards. Don't feel bad. D&RGW is a "best case" for narrow gauge railroad construction. Many narrow gauge railroads' trestles used smaller dimensions, and some of them used much smaller dimensions for the sills and sway braces. (2"x12" sway braces were common on some lines.)
The same applies to any odd widths left over when you cut your posts. If you realize that you'll have enough of a particular width to use for all of your sway braces or for all of the crosspieces that hold the bents together, that's fine as long as you're consistent.
What If I Don't Have a Mill or Even a Table Saw? Of course, many of you can mill wood in your shop; you're ahead of me already. On the other hand, some of you are, frankly, in no danger of ever owning or learning to operate a table saw. There's no real reason you can't buy the lumber, ask a friend who's handy with this sort of thing to slice up a bunch of boards for you to the necessary dimension and do the rest of the project yourself.
Note for O-Gauge-Outsiders: Technically, trestles for your trains should use 1/4" posts and sills, which may require you to be pickier about your source of materials and tools than Large Scalers. Consider that most three-rail O-gauge trains are a little undersized anyway, and if you use trestle components that are too large, you will be reducing the apparent size of your trains even more.
If you are an O-Gauge-Outsider who has had success building trestles for your trains, or if you just want to be kept appraised of any more developments in this area, please contact us so we can keep sharing information.
Once you decide what width of lumber you will be using, you're in a position to start planning your jig. When you begin planning, all the most critical decisions are made in the top six or so inches of the trestle bent. This starts with the "cap," the highest horizontal member of each trestle bent. Your cap will probably be somewhere between 6" and 8", depending largely on what kind of trains you plan to run. A typical D&RGW trestle cap was 14' long (although I've seen some diagrams in which the caps seem to measure about 11'8"). Again, the measurement of your model cap depends on the kinds of trains you're running:
Kind of train you run most often:Recommended Cap Length: Bachmann Shay or other 1:20.3 trainsBetween 7" and 8.25" LGB mogul, Bachmann starter set, or other 1:22.5 trainsBetween 6.5" and 7.5". AristoCraft, USA, or MTH trains6", especially if you're using 3/8" posts. Once your caps get below 5.5", though, it gets harder to assemble the trestle together in the "field."Once I thought I knew what dimensions I wanted for my cap and posts, I started assembling the materials for my jig. In my too-cluttered garage, I found a piece of 3/8" plywood that was left over from a previous project, cut nice and square to about 18" x32". I also brought out several long strips of wood from my fence-board slicing experiment, so I could lay them out on my "jig-in-progress" and get an idea of how they would work. Every time I thought I had the measurements right on my jig, I laid some pieces of wood on the plywood to see if what I was designing was mechanically feasible and or attractive. All of this "hands-on" fiddling would be unnecessary for someone with greater confidence at this sort of thing, but it helped me visualize things and tweak my final measurements.
On a D&RGW-style bent, the distance between the inside two posts is easy to figure - each inside post should be centered under a rail, 45mm apart (1.775"). On this example, the angle of the center posts is also easy to figure - they're vertical. So you can easily use a square to draw their path on your jig.
Now you need to figure out where your outside posts start, and how much they slope. You want the cap to poke out beyond each post at least one post's width. So if you are using 1/2" posts, you need to leave 1/2" clearance or more at each end of the cap. The illustration of the cap and posts above is based on a 7.5" cap. You can tell that this gives you plenty of room to work with. If you haven't already sliced up some wood to try things out with, download the the full-sized picture, set it to print at 7.5" wide on your printer, then cut out four long 1/2" wide strips of paper to work with as you try to visualize your future setup.
As I worked with the D&RGW drawing, I realized that certain things were a little "off," including the slope of the outside legs, which is slightly exaggerated. For an 18" trestle, this wouldn't be so bad, I suppose. But if you built a 3' trestle that used this slope, the base could easily get wide enough to be unmanageable.
In my experimentation with my posts, I found that I was most satisfied when my outside posts angled away from the center posts between 3/4" - 1" per foot. Whatever slope you settle on, you have to stick with that throughout any single trestle on your railroad - you can't change slopes within a trestle.
By now you should have all the information you need to start outlining things on your "jig." Once you have a good outline, screwing little blocks of wood on to keep those pieces aligned while you zap them with your brad gun is the next step.
On a real trestle, the bottom ("mud") still comes first. On a garden railroad, though, we work from the top down. The D&RGW plan says that the sill closest to the cap should be between 16' and 20' below it, and other sills should be 20' apart. That said, most folks go on the closer side, not the maximum, because more sills makes for more apparent detail on the trestle. Before you decide exactly where these things should be, you should dummy up a bent or two and experiment to see what looks right to you. Here are the D&RGW guidelines, transferred to various scales and rounded off to the nearest 1/4".
Kind of train you run most often:Distance From Cap to First Sill:Other Sill Distance Maximum: Bachmann Shay or other 1:20.3 trains9.5" to 12"12" LGB trains, Bachmann starter sets, or other 1:22.5 trains8.5" to 10.5"10.5" AristoCraft, USA Trains, or other 1:29 trains6.5" to 8.25"8.25" MTH trains or other 1:32 trains6" to 7.5"7.5"How many sills you use depends on how long your trestle will be. Most garden railroaders don't put bottom sills on most bents, since they are most interested in the bents aligning at the top (where they meet the roadbed), and the way things align down below is secondary.
You don't need to plan the length of your sills - that will be dictated by their location on the bent. However, you will want to extend the ends of each sill at least one post width (I'd recommend 2) beyond the vertical post, so you have room for the cross-pieces that tie the trestle bents together once they are in place.
Also, you won't need to plan the length of the diagonal "sway braces" - that will be dictated by everything else, and will vary depending on what part of the trestle bent you're working on. The only other thing you need to know about the braces right now is that many trestle plans show them extending too far. When you actually add them, don't let them extend much, if at all beyond the posts. Again, you need to leave room on the sill for the cross-pieces to go on. On the title photograph, the builders have gone one step farther - they have attached the diagonals only to the posts, which saves a little bit of wood and makes the bents easier to handle for moving and setup (a big issue when you're installing hundreds, as they did at that site). I think it creates a nice appearance but some purists would probably cringe.
Once you create an outline for what the bents will look like, then you create your "jig." Transfer your measurements onto a wide board or a piece of plywood. Some folks just draw the bent on the board, then tap in a bunch of finishing nails so the components have to go the right places. This is good for an experiment or trial run, but the pressure from the brad gun will loosen things up before long. For long-term use, most folks screw blocks onto the board for a more "foolproof" guide.
The photo to the right shows a jig that started out as a 4-post-jig (see the line drawings) but was converted to a three-post jig for the trestle on a children's railroad. The oversized sills are just there to help me locate the blocks properly before I refasten them.
Generally you won't need to show your sway braces on your jig - it's pretty obvious where they go once you have the posts and sills installed. But if you do want to show them for some reason, be sure to show only half of them - the ones you install from "this side." That way you have less chance of having some bents where the sway braces go one way and some where they go the other.
Make a few bents and line them up (detailed steps are below). Make certain they're symmetrical so it doesn't matter which way you have them turned when you line them up. Take them out into your garden railroad and make certain they will fit where you want to use them and that they will support your track or fasten to your roadbed the way you think they will.
When you think you're ready to go, it's time to start "ripping" cedar in earnest. While you're at it, cut a bunch of "posts" to a length that is a couple inches inch longer than you think you will need them to be. This will give you extra "room to work with" if things have shifted around since you started this project. Garden railroaders who are doing a really big project where the final measurements are unknown often leave 6"-12" extra. It's a lot easier to cut off extra material once you are on the "job site" than it is to add.
Try to cut the shorter pieces, such as caps and sills, from any scraps, although you may need to sacrifice a long piece to get started.
Also, depending on how you decided to represent the cross pieces that hold the bents together once they're installed, you may need to cut some other lengths of wood.
When you have more bents than you can possibly use on the first bit of trestle you plan to build, stop.
Ordinarily you will build your final trestle on site, but there may be times when it makes sense to build it all at once, such as the trestle for the "demo" railroad shown to the right. This one used the unprototypical three-posted version of the jig shown above. We screwed the caps to a 5/4"x6" piece of wood to make the whole thing stable enough to haul over a thousand miles and set up multiple times.
When you take your trestle bents outside, you'll probably want to take:
Put on long pants or figure out some other way to protect your knees. Take your bents, other pieces, and tools to wherever you're going to install your trestle. Some folks like to start in the middle and work their way in both directions. Wherever you start:
On the other hand, if you're using long pieces of wood to represent crossbars, you should try temporarily laying the pieces where they will need to go every so often, even though you can't really attach them until you've got a lot of the trestle run. This gives you another way to check the vertical alignment of your trestles - if the sills seem to be going up and down underneath your crossbar, you may have a problem.
If you haven't taken steps to protect the base of your trestle from moisture and frost heave, please make a note to do so between now and bad weather.
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